The standard first-line treatment for HER2-negative advanced G/GEJ adenocarcinoma has been platinum-based agents plus 5-fluorouracil (Cheng et al., 2019; Lordick et al., 2022), but these have yielded unsatisfactory results, with median overall survival (OS) of less than 12 months (Al-Batran et al., 2008; Kang et al., 2009; Chen et al., 2018), making the exploration of new therapeutic approaches urgent. This evidence concerns the gene ERBB2 and gastroesophageal junction adenocarcinoma.